The invention relates to a device for passing electric current through a wall subjected to excess pressure on its inner side, in particular the wall of a pressure gasifier for coal. In a known type of device the wall is formed with an aperture which accepts a sleeve through which a conductor passes, which sleeve is braced against the inner side of the wall by an integral collar.
One of the chief areas of application of the invention is in the conducting of current to dust arrester installations, known as electro-filters, of pressure gasifiers for coal. If these electro-filters are arranged before the gas scrubber, they are subjected to relatively high temperatures, for example, around 600.degree. C. The temperature is higher than when the electro-filters are arranged after the gas scrubber, although even in this case high temperatures still prevail. Also, coal pressure gasifiers operate at pressures of the order of 20 atmospheres. A device for passing electric current through a wall of an electro-filter is thus subjected to pressures and temperatures of this scale, and is additionally mechanically stressed in the wall by forces transmitted through the current supply cable.
The above-mentioned known type of device usually has a sleeve consisting of ceramic material which directly encloses the electrical conductor and has the job of preventing voltage flashovers. This device is only suitable, however, for relatively low pressure of around 1 atmosphere and is thus not suitable for use in pressure gasifiers for coal. It also has numerous other disadvantages.
On heating, stresses are produced in the material of the sleeve due to the differing coefficients of thermal expansion, which stresses are still further increased by the pressure difference and cannot be dispersed in the material. Moreover, because of its low impact strength, ceramic material is only serviceable for use in a high pressure system under certain conditions. Also, no possibilities for repair exist for a damaged insulation, and the device has to be completely removed and sent to the manufacturer when damaged. The known device is additionally susceptible to shock and strain and thus can only absorb low mechanical forces transmitted through the cable.
The known device also cannot be used under high pressure because, amongst other things, on breakage of the collar the entire device flies out of the aperture in the wall and a rapid pressure drop ensues, which is unacceptable. Moreover, the ceramic mass tends to form hairline cracks which can lead to indifferent operation.
The result of these disadvantages is that hitherto it has not been possible to use electro-filters reliably in coal pressure gasification processes, and for this reason no suitable cleaning of the gasification gas could be provided directly before or after the gas scrubbers.
The essential task of the invention is to provide a device of the type referred to in the introduction which can withstand the combined stresses of pressure differential, heat expansion, and the forces mechanically exerted by the cable.